Conventional toilets generally have a flush valve that is manually actuated by a user, which when opened causes a predetermined amount of water to flow from toilet tank into the toilet bowl, thereby initiating a flush of the toilet bowl. In conventional toilets, the size of the flush (i.e. the volume of water that flows into the bowl from the tank) is constant. The tank includes a refill valve which is used to refill both the toilet tank and the toilet bowl after the flush. The refill valve is typically controlled by a buoyant member such as a ballcock or float. When the water level in the tank drops during a flush, the float falls with the water level and opens the refill valve. The refill valve remains open until the tank is filled to a preset level, at which point the float causes the refill valve to turn off. A portion of the water provided by the refill valve is generally diverted into an overflow tube, and is used to refill the bowl after a flush. Thus, in a conventional toilet, the refill valve must be calibrated so that the bowl refills to the proper level in the time it takes for the tank refill to the preset level.
In recent years, dual flush toilets have become more popular. As used herein, the term “dual flush toilet” means a toilet with two different flush sizes—a partial flush for disposal of liquid waste, and a full flush for disposal of solid waste. The full flush uses approximately the same volume of water as the flush in a conventional toilet. The partial flush uses less water, in some cases approximately half as much as the full flush. However, the different flush sizes in a dual flush toilet creates difficulties for refilling the bowl after a flush. Because the partial flush uses less water, the water level in the tank does not fall as far as it does in a full flush. Thus, the tank fills up faster after a partial flush than after a full flush. In other words, the refill valve is open for less time after a partial flush than after a full flush. However, the bowl is equally empty after both partial flushes and full flushes. The problem that thus arises is that bowl must be refilled to the same level after both partial flushes and full flushes, even though the refill valve is open for different durations of times depending on the flush that just occurred.
Further, in siphonic toilets commonly found in the U.S., it is important to refill the bowl to the correct level after a flush. If the water level in the bowl is too low, it may not block sewage gasses from entering the room from the sewer. If the water level in the bowl is too high, then water is wasted. Since the main purpose of dual flush toilets is to conserve water, simply calibrating the toilet to fill to the correct level after a partial flush is not a satisfactory solution because then the bowl would be overfilled after a full flush (since the refill valve is open longer after a full flush). Similarly, simply calibrating the toilet to fill to the correct level after a full flush is not a solution because then the bowl would be underfilled after a partial flush (since the refill valve is open less time after a partial flush), potentially allowing sewage gasses into the room.
Accordingly, there is a need for a device that refills the toilet bowl to the same level after both partial flushes and full flushes in a dual flush toilet. It is also desirable that such a device has minimum components and is easy to operate.